Geology: Photographs.

[Eu_citzen]

During my fieldtrips I often find something I like to photograph. I collect "geological pictures" from my trips in Sweden.
Thought I'd share some of them.

This one is interesting. To the left we have rhyolite, a volcanic rock. To the right of the big "bend" we have serpentinite. A metamorphic rock.
The "bend" (or deformation) is possibly a result of the alteration of the original rock to serpentinite. Simply because it increases in volume when it alters.



I love samples which are small enough to fit into the palm of my hand and still tell a little history.
This little metarhyolite shows what "faults" can look like in a small scale. (notice the red band in the lower right)




Breccia is something I don't see to often here. It is basically a fractured rock that got glued together.


Gneiss is also a metamorphic rock. Often with distinct "bands". This was a large boulder transported during the last ice age.


Here is a cool photo of a large rock wall. Also made of gneiss, from near the coast. The formation is called "Coastal gneiss".
I know, there seems to be a lack of fantasy for some names.


More gneiss, this time granitic gneiss. Notice the pegmatite vein near the middle. Thought it was neat.


Antiform, a little larger type. Basically an "upwards" fold, well part of in this case.


An intrusion of basalt. About 4 metres thick. If you look closely you can see pegmatite and quartz veins, to.


During the last ice age the ice sometimes "scraped" on the bedrock. It could then create "scratches", like those in the picture.
They help indicate which direction the ice had. Compass for size.


Sometimes you run out of time when you find something cool.
Here is one example, I never had enough time to examine it closely but think this is an ancient fault:


And to finish this off, a shear zone. The shear zone cut the vein in two.

 

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[DDancer]

Yep those are sedimentary formations. Reminds me of the Painted Desert up on the Navajo Reservation in Arizona.

As to your first picture EU, the slim compressed bands just off center and up of the stone. I dont think its a shear though as the deformation shows no offset.

 

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[Eu_citzen]

Yep those are sedimentary formations. Reminds me of the Painted Desert up on the Navajo Reservation in Arizona.

As to your first picture EU, the slim compressed bands just off center and up of the stone. I dont think its a shear though as the deformation shows no offset.

The offset is difficult to see in uniform granite, since there are no markerbeds, enclaves or similar to show any offset. All we can see is the band.
There is a major shear zone 1 Km east of it with the same trend; 300NV. I think they're related.

 

[DDancer]

In uniform granite sure however the patterns are offset in shear, compare the upper and lower portions. Shear also often shows large granulation in uniform granites as a result of heat metamorphism due to slippage or intrusion of hydrothremal events working up thru the cracks. They, slips, can be small or large and often are distinct with vugs unless its high compression. Thats my experience. Your more experienced here so I differ.

 

[Eu_citzen]

Nah, keep at it brother. Appreciate it. My guess surely has some loose ends. That's why "probably" is there.
Smaller structures tend to mirror larger ones, that's another reason for my guess.

The observations you have are correct for ductile to semi-ductile shear zones. But you know, it's never simple, because we've got brittle shear zones to.
The brittle ones look very much like faults.

Any fabrics are difficult to see here, the actual width of the pictured deformation zone is approx 2mm.